Lab test for glucose and pancreatic hormones

What tests are used to diagnose diabetes

Fasting plasma glucose OR 2-h plasma glucose/OGTT OR A1C OR symptoms of hypo/hyperglycemia and random plasma glucose

What is fasting plasma glucose

Measuring blood after fasting for >=8 hours; indicates impaired fasting glucose

Range for FPG

Normal <99; prediabetes (indicates impaired fasting glucose) 100-125; DM ≥126

What is 2-h plasma glucose during 75g oral glucose tolerance test

Measuring clearance of glucose in blood after ≥8 hr fast + after consuming 75g of glucose in water; indicates impaired glucose tolerance

What is range for 2-h PG after OGTT

Normal ≤ 139; prediabetes (impaired glucose tolerance) 140-199; DM ≥ 200

What is HbA1c

Measures the glycation of glucose in EDTA or heparin blood

Range for HbA1c

Normal ≤ 5.6; prediabetes 5.7-6.4; DM ≥ 6.5

What is the consideration for HbA1C

The test needs to be done through a CERTIFIED or standardized assay

What is random plasma glucose

No fasting needed; measure glucose in NaF plasma in patient with DM symptoms (polyuria, polydipsia and unexplained weight loss)

Range for random plasma glucose

Normal ≤ 199, DM ≥ 200

Why is NaF tube needed to measure blood

NaF INHIBIT glycolysis of glucose in RBC or PLT

What tests are used to MONITOR DM

HbA1c, NGSP: affinity chromatography, capillary electrophoresis, HPLP, enzymatic assay, immunoassay

How does Boronate affinity chromatography work

Boronate bind to glucose on glycated RBC → Non glycated RBC elute = first peak → Glycated Hb elute = second peak

What is enzymatic assay for glucose

Protease break down glycated Hb into glycated peptides and amino acids add POD to get color

Which HbA1c methodology can detect hemoglobinopathy

CZE, Cation exchange HPLC ONLY

What is fructosamine

Measures glucose bound to albumin; average blood glucose of 2-3 weeks; used for patients with SEVERE hemoglobinopathy

What is the characteristic of insulinoma

High insulin and C-peptide with no sulfonylurea

What is characteristic of exogenous insulin

High insulin, low peptide C

What is characteristic of sulfonylurea use

High insulin and peptide C with sulfonylurea use

What autoAb test are used for DM

Anti-GAD65, IA-2, ZnT8; used for SCREENING in patient with strong history of T1DM

What are the test for gestational DM

50g glucose challenge test → Screening; 100g OGTT → diagnosis

What is 50g glucose challenge test

No fasting; drink 50g of glucose in water and test plasma glucose after 1 hr; if <140 normal

What is 100g OGTT

8 hour fasting; test plasma glucose before loading → Drink 100g glucose in water → Test PG at 1,2,3 hr

Range for 100g OGTT

Fasting <95, 1h <180, 2h <155, 3h <140; if at ANY point glucose is above the value = GDM

What tests are used for neuroendocrine tumors

Gastrin, glucagon, VIP (in EDTA), somatostatin (in EDTA/heparin)

What are the fasting time for neuroendocrine tumor lab test

VIP 4 hrs; glucagon 8-12 hrs; Gastrin and somatostatin: 10-12 hrs